Thermostat



June 3, 1930. p, s, MARTlN 1,760,878

Y THERMOSTAT Filed July 16, 1925 2 sheets-sheet 1 f Z7 /7 Z4 15 75 au;

Jue 3, 1930. P. s. MARTIN 1,760,878

THERMOS TAT Filed July 16, 1925 2 Shets-Sheet 2 ,Perry MaZn,

Patented .une 3, i 1930 'snr PERRY S. MARTIN, OF HARBISONBRG, VIRGNI THERMOSTAT Application led July 16,

This invention relates to thermostats and has for its principal object the provision of a thermostat suitable for use Where quite direct adjustment is desired.

A further object of the present invention is the provision of a thermostat utilizing the bowing of a metal strip in which, with increased heat, the supports of the bowed elements are drawn together thus increasing the lateral movement of the center of the bowed stri Apstill further object of the invention is the provision of a thermostat utilizing a plurality of expansible bars so held that their free ends will expand in opposite directions and in which said expansion will draw together the supports of a bowed member which bowed member may also be an element having a fairly large coehcient of heat expansion whereby7 the amount of lateral bowing will be the sum of the expansion of both members.

In a number of diderent arts a dir-ect thermostat is desired and in many cases it is quite important that the thermostat shall act quickly upon a very small change in temperature and it is important above all things that these thermostats shall operate with extreme Y consistency. As an example of the use of such thermostat I mention incubator struc-, ture as while obviously suitable for many other uses my invention is primarily intended for the production of a thermostat suitable for use in incubators where the permissible range of temperature is very low.

In the drawings Figure 1 shows the principle of the invention in its simplest form.

Figure 2 shows a simple structure illustrating the spirit of the invention with the use of opposed bowed elements.

Figures 3 and 4 are a plan view and cross section respectively of one form of my invention.

Figures 5 and 6` show slightly modified commercial forms.

Figure 7 is a section on line 7-7 of Figure 5. l

Figure 8 is a modified form of the invention.

1925. Serial No. 44,045.

Figure 9 is a section on line 9 9 of ure 8.

Figure l0 is a detailed section showing the clip on the-rod for securing the expansion tubes.

In the simplest form of the invention as shown in Figure l there are two supports A and B, from one of which extends an expansion member such as E which is secured to A and extends toward B. At the free end of E a member S is secured and this link member preferably runs directly backward parallel to E, ending `with the anchor or hook F a short distance away from the support A, or, to be more exact, the length of the element S is such that it willvjust clear the support A when the expansion element E is chilled to the greatest extent, i. e., to the lowest temperature, to which it will be subjected. In the wall or support B, there is a second or fixed anchor G in the form of a 'notch or recessed portion Vadapted to permanently receive one end of the flexible bowed element H, while the other end of this bowed element H is permanently retained within the hook F.

The anchor G is fixed and the distance bef tween A and B is fixed. rlhe anchor F however, moves toward the anchor G if-the element E has a greater coefficient of expansion than the link element S, which is the case, E being preferably of forged zinc for example, which expands l/5O of an inch per 100 feet for each degree of increase intemperature, and the link element being of invar, platinum, glass, porcelain, steel or other material hav-V ing a low rate of expansion. The bowing element H may be cf steel inwhich case as the element E expands the center of H will bow upwardlyin direct ratio to the closing in of the anchor F toward the fixed anchor G irrespective of the temperature of the element H. It would naturally be preferable to make the bowing element of aV material which itself had ay high coefiicient of expansion as in such structure the amount of lateral, o r in this case, upward movement of the center of the bowing element H would be increased, over and above the amountcaused by the reduced distance between the two anchors, lby the v amount of bowing caused by the linear expan Figsion oit' the sheet or strip H and consequently l preferably make this sheet of such a material as spring brass so that it may readily force up the link L connected to the lever M so as to cause downward movement of the'rod R which may operate any desired element to beA under the controler'l the temperature in the neighborhood of the expansive element E.

ln the diagrammatic, simple form shown in Figure 2 the two bases are replaced by' a sin# gle base member C, one end .of which is equivalent of the support A and the otherrend is equivalent to the support B. As shown, there are two expansive elements E each secured as diagrammatically illustrated, by a bolt D to the steel base C, each zinc expansive element having at its far end a link element S also ot steel and forked as at F to form a rounded hook or jaw in which is pivotally received the rounded end of the spring brass bowingstrip H, the other end of whichvis similarly received in the iorked end K o a brace or other support B or A secured to the steel base C and corresponding to the lined anchor G of the simpler form. ln this device the base may be horizontal or vertical and may be made of steel, as stated, or obviously of Glass, porcelain or any other material.

As the device as a whole is subjected to increase ot temperaturathe base and the link elements S expand but slightly while the main primary elements E expand at a rather high rate which has the eiect of drawing the movable anchors F toward the i'ixed anchors l increasing the amount of bowing of the ilexible bow/'ing elements H, and if these are of brass as preferred, the increase in tempera ture extends these elements as well, so that a very considerable amount of bowing may be ad with a. slight change in temperature and Y e increase in distance apart of the cent-ers the two bowing elements H is utilizedto operate a damper, switch, Vvalve or any other controlled element. l

Y 'ln the form shown in Figures 3 and 4e, the primary expansion members and 11 are each preferably channel shaped and of eXactly similar size whereby innestingone of the Y side flanges of each is between the two sidelang'es of the other channel member. I find it convenient to make the two channels of zinc as this metal has a quite highcoecient ofA lin-ear expansion.

Gire/of the channels 10 is closed by a steel clip 12 and the opposite end of the member 11 is ,closed bya similar steel clip 14. These tivo steel clips are rigidly secured to each other by a pair of steel rods 15,' steel being chosen tor its strength and for its relatively low coemcient-o't expansion. To the other end ot the zinc channel 10is secureda steel clip 16 and to the other end or" the zinc channel ll'f sl'eel clip l? is securedandas nearV a similar centrally as possible a Vsteel vrodV passes thru theclip le to a steel end piece and thru the clip 17 to a similar steel end piece 21. The length oi these rods, that is, the rod 24 rigidly connecting clipV 16 and end piece 20 and the rod 24 joining the clip 17 with the other end piece 21, is such that at the hottest temperature to which the thermostat will be subj ected', the end pieces 2O and 21 will just clear the end pieces 16 1'!" through which, respectively, the rods 24rand 22 t'reelyslide. Secured in any manner to the end pieces or anchors 20 and' 2-1, but preferablyA piv'oted Vas illustrated, are strips 26 and 2? or resilient metal preferably ot spring brass. lt is not necessary that the strips 2G and 27 have a high co-eili 'ent et expansion as they will bow outwardly in any event with the structure,recited. It is advantageous, however, to have these strips of a metal having in addition to a reasonable degrec oi strength and resilience, a high coeilicient of expansion as this will itself increase the lateral movement and l lind s )ring brass admirably suited but ai" Leu clips 1G and 1T. These latter being; rigidly connected throug'i the non-e2pandinosteel rods 22 and 2% als f protected lfrom directheat by thechannels and clips, cause the two `end pieces 2O and 2l to approacheach other thereby causing simultaneous bowing of the tvro secondary, expansion VelementsY 26 andV 27 which engage in any desired manner the device to be worked bythe thermostat diagraminatically'illustratedby the members 29 and SOslidabl-e supporting sleeves31, these parts being truly diagrammatic landadded solely for the convenience of illustration. Ob viously the greaterthe amount of expansion of the Zinc ychmnels the greater the separation of the governing,` mechanisms 29 and 3() and in case of a chilling of the thermostat the conraction oit the primary thermostat bars 1() and 11 cause the separation of the end pieces 2O and 21 thereby tending to straighten the secondary thermostats and 27' withY a con'- sequent drawing together ot the members 2Q and 30. y 1 Y,

In Figures 5 and 8 I have shown two com; mercial forms of my thermostats,A the former bei-ng particularly advantageous where aV rather powerful thrust is required and the latter being advantageous wherea considerable amountot movement is desired. ln the form shown in Figure 5 the primary expan' the same time l wish Vit distinctly understood that these strips may its members 45 in order to provide as much ex posed space as possible between the anchor' 44 and the clip 42 as this is advantageous in incubators where the heat which affects the primary expansion members is radiated heat. Gbviously an equivalent method of obtaining large area of a'ected surface on the primary expansion member would be by making the secondary expansion member narrower and thicker and carrying the anchors further apart. The central rod 47 is preferably headed at one end and threaded at the other and has the usual nut 48 so that a very close adjustment may be made in order that we may obtain at any given temperature any given amountl of bowing.

The connections between the rod and the primary expansion members 40 may be loose or tight and this applies equally well to the connection between the anchors 44 and the secondary expansion members 45 but at least one of these joints should be loose in order that when the thermostat is chilled there shall be no stress of any kind on the parts. I find in practice that it is most convenient to have a friction connection between the anchors 44 and the spring elements 45, to make a positive connection at the headed end of the rod and the adjacent clip 42. A further very im ortant feature is that b this rovision p Y the nut 48 may be loosened and the thermostats shipped flat and entirely free from stress at any temperature.

The form shown in Figure 8 is similar in general to the form just described and like the other forms contemplates no bending of any kind of the zinc members. The center rod being exactly similar to the rod of the modification shown in Figure 5, is given the same numeral 47. The primary expansion tubes, however, are preferably made each of two pieces, for example, as channels 50 and 5l which may be nested as in Figure 4 but preferably are made with one of the channels, such as 50, wider than the other channel. The end clips 52 are of rather sturdy construction so that neither the head of the rod or bolt nor the nut 48 may bite even slightly into the clip. In this form I have a second steel clip 54 loosely mounted on the rod 47 and having anchor ends 55 embracing the flat body portion of the zinc channels. The center clips 56 areformed of Hat sheet metal Vbent downwardly about the base of the channels',.ear'riedreversely as at`57 over the top of the channels and ending in an anchor 58, exactly similar in purpose and effect to the anchors 44'.

In this modification the clip 54 acts as a hinoe and as primary expansion members, i. e., theA zincchannels, expand, they naturally open at the center drawing the two` anchors 58 toward one another and causing the spring members 60, whether expansive or not, to ytake up the bowing at this point, therefore relieving the Zinc channels of any tendency toward distortion or even bending and utilizing all of the straight thrust which is added to if the spring members are of brass or other high expansion material as is preferred.

rIhe advantage of this form is that a very slight increase in temperature will give a large amount of movement at the center. It also has the advantage of the modification shown in Figure 5 in that the thermostat may be shipped absolutely flat by releasing the nut 48. In some ofthe thermostats made in this form it has been found convenient to omit the clip 52 entirely and to seat the head of the rod 47 and the nut within the hollow of the clip 54 but the disadvantage of this is that the wear, even tho very slight, is Suthciently great to require rather frequent adjustment of the position of the nut.

l/Vhat I claim is l. In an Yincubator thermostat, two elongated high expansion members in tandem relation, a low expansion rod connecting the distant ends of the two high expansion members, clips extending from the proximate ends of the high expansion members backward toward the ends of the rod, and a spring engaging each clip,'said rod serving not only to hold the members assembled but also acting to limit separation of the far ends of the two members. y

2. The device of claim l in which the two members aretubes, the rod is inside of the tubes and the spring is outside of each tube.

3. The device of claim l in which the members are each of two channels nesting to form a tube, the four channels are hingedly connected to the rod which is inside of the two tubes, and in which thereare four clips each extending on the outside of one ofthe four channels, and two springs between t-he four clips.

4. The device of claim l in which one end of the rod is adjustably secured to one member so that by changing such adjustment the amount of lateral movement of the center of the spring can be controlled.

5. In an incubator thermostat, two tandem tubes of high expansion material each consisting of two opposed nesting channels, a low expansion rod thru both tubes, means securing the rod to one end of each of the four channels, and means for connecting theY proximate opposed ends of the two channels on each side of the central ro-d whereby when the device is heated the ends of the channels of each tube, farthest fromlthe rod ends, will separate laterally, while the proxiniatevends of the tubes approach each other longitudinally.

6. The device ofclaini -5 in which the connecting means are springs of high expansion Y material thereby increasing materially the lateral distance between the springs when the incubator temperature increases.

7 The device of claim 5 in which the length of the rod is adjustable whereby the lateral deflection of the connecting means may be altered at any chosen temperature.

ln testimony whereof I aliix my signature.

PERRY S. MARTIN. 

